Power supply interconnect structure of semiconductor integrated circuit

ABSTRACT

A power supply interconnect structure of a semiconductor integrated circuit includes a single borderless stack via electrically connecting power supply interconnects of two different interconnect layers to form a connecting portion of the interconnects, and a multi-stack via functioning as another connecting portion of the interconnects, which electrically connect the power supply interconnects, and having a wide pad portion. The single borderless stack via is located in an interconnect region with high signal interconnect density. The multi-stack via is located in an interconnect region with low signal interconnect density. This increases interconnection efficiency in the region with the high signal interconnect density to improve interconnection characteristics. This enables reduction in an area of a chip and increases compatibility to an EDA tool, thereby improving IR-DROP characteristics.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of PCT International ApplicationPCT/JP2009/004119 filed on Aug. 26, 2009, which claims priority toJapanese Patent Application No. 2009-009972 filed on Jan. 20, 2009. Thedisclosures of these applications including the specifications, thedrawings, and the claims are hereby incorporated by reference in theirentirety.

BACKGROUND

The present disclosure relates to power supply interconnect structuresof semiconductor integrated circuits in which power supply interconnectslocated in different interconnect layers are electrically connected byvias.

Conventionally, in a semiconductor integrated circuit, a power supplyinterconnect structure using a multi-stack via is known as a structurein which two power supply interconnects located in two differentinterconnect layers are electrically connected by a via. Theconventional power supply interconnect structure will be described withreference to FIG. 11.

FIG. 11 is a cross-sectional view of an LSI interconnect layer, and FIG.13 is a top view of the LSI interconnect layer. In these figures, L1-L4denote first to fourth interconnect layers. Reference character 51denotes a first power supply interconnect located in the firstinterconnect layer L1, reference character 52 denotes a fourth powersupply interconnect located in the fourth interconnect layer L4. Whenconnecting the first power supply interconnect 51 to the fourth powersupply interconnect 52 as a single power supply interconnect, the secondinterconnect 53 and the third interconnect 54 for connecting the powersupply interconnects 51 and 52 in the second and third interconnectlayers L2 and L3. A first to third vias 56, 57, and 58 are located inthree insulating layers I1-I3. The second and third interconnects 53 and54 and the first to third vias 56-58 have the forms shown in the topview of FIG. 13. The vias 56-58 are multiple vias (double vias in thefigure) in which two vias are closely arranged in a vertical directionin FIG. 13. The interconnects 53 and 54 connected to the multiple viasare widely formed in vertical and horizontal directions to include thedouble vias inside when viewed from the top.

As can be seen from FIG. 11, the first via 56, the second interconnect53, the second via 57, the third interconnect 54, and the third via 58in a single vertical line are stacked to form a single multi-stack viain the same vertical line. Using this multi-stack via as a single unit,five units are formed in the figure. There units connect the first powersupply interconnect 51 to the fourth power supply interconnect 52,thereby forming an electrically connected single power supplyinterconnect.

Furthermore, Japanese Patent Publication No. 2003-86681 teachescalculating the amount of a current flowing between the first and secondpower supply interconnects 51 and 52, calculating the minimum number ofnecessary units from the amount of the current, and cutting unnecessaryvias to increase interconnect resources. As exemplified by FIG. 11, inJapanese Patent Publication No. 2003-86681, a signal interconnect 62 ofthe second interconnect layer L2 is located between each two of the fiveunits. This structure increases interconnection efficiency to improveinterconnection characteristics.

Different from the above-described power supply interconnect structure,borderless vias have been developed as an interconnect structure ofsignal interconnects as shown in SEMI Japan, Text Book of SemiconductorProcess, pp. 362-363. Like the multiple via shown in FIG. 13, theborderless vias do not have pad portions, which are excessive wideinterconnect regions, and are the mainstream of a design for manufacture(DFM). With the development of manufacturing processes ofsemiconductors, vias and interconnects can be accurately formed inpredetermined positions. Thus, a borderless vias is set so that thehorizontal and vertical lengths are substantially equal to thehorizontal and vertical lengths of an interconnect to which theborderless via is connected.

SUMMARY

In a power supply interconnect structure of a semiconductor integratedcircuit, a large number of multi-stack vias are located to addressIR-DROP and electromigration (hereinafter referred to as EM) to reducevoltage drop before reaching a target cell and to prevent disconnectionat vias.

However, when considering highly integrated design, which is a point ofview different from solution to IR-DROP and EM, the multi-stack via maybe insufficient to maximize or optimize interconnection efficiencyaround the vias. This will be described in detail with reference to FIG.12.

FIG. 12 is a partial enlarged view of the multi-stack via and theinterconnect in the region circled in FIG. 11. In the figure, referencecharacter 60 denotes an interconnect track. The figure shows fourinterconnect tracks 60. Although two interconnect track 60 arepositioned between multi-stack vias, only a single interconnect 62 canpass between the multi-stack vias to comply a separation rule equivalentto an interconnect width, since projecting wide pad portions 61 and 61exist in the interconnect portion.

This is significant from the top view of FIG. 13. In the figure, whenusing six horizontal tracks and three vertical tracks, each separationwidth to the closest horizontal and vertical interconnect tracks isoriginally a distance So to the vias 58 near multiple (double in thefigure) vias. Due to the existence of the pad portion 61 of theinterconnect 54, the separation width is the distance Sx which isshorter than the distance So by the length of the pad portion. Thisdisables interconnection to tracks 1 and 3 in a vertical track, andinterconnection to tracks B and E in a horizontal track, which areoriginally possible. As a result, interconnect resources available for asignal interconnect are restricted to zero in the vertical direction andtwo in the horizontal direction, which are originally two in thevertical direction and four in the horizontal direction.

The present inventors focused on borderless vias which are employed forthe signal interconnect as a power supply interconnect structure of asemiconductor integrated circuit, and studied using a single via forpower supply interconnects and using a stack borderless via. In thepower supply interconnect structure having the single borderless stackvia, since there is no pad portion included in a multi-stack via,interconnection efficiency increases to improve interconnectioncharacteristics, while solution to IR-DROP and EM are concerns. Withrespect to IR-DROP, a conventional multi-stack via structure shown inFIG. 4B has a great parasitic resistance, since power supplyinterconnect length to the target cell 40 is long. On the other hand,single borderless stack vias shown in FIG. 4A have shorter power supplyinterconnect length to the target cell 40, since the single borderlessstack vias are scattered with larger via-to-via spacing than those ofFIG. 4B and a single borderless stack vias is located near the targetcell 40. Therefore, IR-DROP can be reduced as compared to a multi-stackvia structure. With regard to the EM limited at a via portion, singlevias and multiple vias have the same EM characteristics when the numbersof the single vias and the multiple vias are the same each other.Therefore, the present inventors found that interconnection efficiencyincreases to improve interconnection characteristics while reliablyproviding solution to IR-DROP and EM, even when a single borderlessstack via structure is employed as a power supply interconnectstructure.

From the above studies, it is an objective of the present disclosure toreliably provide solution to IR-DROP and EM and to increaseinterconnection efficiency to improve interconnection characteristics byemploying a single borderless stack via structure for connecting powersupply interconnects of different interconnect layers as a power supplyinterconnect structure of a semiconductor integrated circuit.

Specifically, a power supply interconnect structure of a semiconductorintegrated circuit according to the present disclosure includes powersupply interconnects located in two different interconnect layers withat least one single intermediate interconnect layer interposedtherebetween; and a single borderless stack via configured toelectrically connect the power supply interconnects located in the twointerconnect layers to form a connecting portion of the interconnects.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, the singleborderless stack via forming the connecting portion of the interconnectsincludes single vias located in respective two or more insulating layerslocated between the two interconnect layers, and an interconnect locatedin each of the at least one intermediate interconnect layer, and havinga same cross-sectional shape as the single vias of the insulatinglayers. The single vias of the insulating layers and the interconnect ofthe at least one intermediate interconnect layer are alternately layeredin a same vertical line and electrically connected to form a unit.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, the unit of thesingle borderless stack via includes single vias located in respectivethree insulating layers, and interconnects located in respective twointermediate interconnect layers interposed between the three insulatinglayers.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, multiples onesof the unit of the single borderless stack via are formed. Distancesbetween the units are equal.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, multiple ones ofthe unit of the single borderless stack via are formed. Distancesbetween the units are equal and unequal.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, multiple ones ofthe unit of the single borderless stack via are formed. A first signalinterconnect is located in a region between two adjacent ones of theunits.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, a distancebetween the single borderless stack via and the first signalinterconnect is equal to a distance between the first signalinterconnect and a second signal interconnect adjacent to the firstsignal interconnect.

The power supply interconnect structure of the semiconductor integratedcircuit according to the present disclosure, further includes the singleborderless stack via forming the connecting portion of theinterconnects; and a multi-stack via configured to electrically connectthe power supply interconnects located in the two interconnect layers toform another connecting portion of the interconnects.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, the multi-stackvia includes a plurality of vias located in respective two or moreinsulating layers located between the two interconnect layers, and aninterconnect located in each of the at least one intermediateinterconnect layer and having a pad portion to include the plurality ofvias in the two or more insulating layers inside when viewed from above.The plurality of vias of the insulating layers and the interconnect ofthe at least one intermediate interconnect layer are alternately layeredin a same vertical line and electrically connected.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, the singleborderless stack via forming the connecting portion of the interconnectsis located in a signal interconnect region. The multi-stack via formingthe other connecting portion of the interconnects is located in anon-interconnect region to which a signal is not interconnected.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, the multi-stackvia forming the other connecting portion of the interconnects is locatedin a region of the signal interconnect region having predeterminedsignal interconnect density. The single borderless stack via forming theconnecting portion of the interconnects is located in an interconnectregion of the signal interconnect region, which has signal interconnectdensity higher than the predetermined density.

In the power supply interconnect structure of the semiconductorintegrated circuit according to the present disclosure, multiple ones ofthe single borderless stack via are located in a plurality of places. Adistance between the multiple ones of the single borderless stack via islonger than a distance between the plurality of vias in a sameinsulating layer of the multi-stack via.

As described above, in the present disclosure, the power supplyinterconnects of the different interconnect layers are electricallyconnected by the single borderless stack via. Thus, the structureprovides higher interconnection efficiency than a conventionalmulti-stack via having a wide pad portion, thereby improvinginterconnection characteristics. As a result, a chip area can beeffectively reduced, and IR-DROP and EM characteristics can be wellmaintained or improved.

In a conventional technique, it was difficult to place a signalinterconnect around a multi-stack via on an interconnect track definedby an EDA tool. By contrast, a signal interconnect around a singleborderless stack via can be well placed on an interconnect track toprovide excellent compatibility to an EDA tool.

In particular, the structure of the present disclosure includes the twotypes of the single borderless stack via and the multi-stack via asconnecting portions of connecting the two power supply interconnects.This effectively reduces an increase in combined resistance values ofthe entire power supply interconnect to improve the yield, even when viaopen faults occur.

As described above, in the power supply interconnect structure of thesemiconductor integrated circuit according to the present disclosure,the single borderless stack via structure is employed. This increasesinterconnection efficiency to improve interconnection characteristics,reduces a chip area, and well maintains or improves IR-DROP and EMcharacteristics. In addition, compatibility to the EDA tool increases toreduce turn around time (TAT).

In particular, the structure according to the present disclosure alsoincludes the multi-stack via as a connecting portion of interconnects.This effectively reduces an increase in the combined resistance valuesof the entire power supply interconnect when via open faults occur toimprove the yield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a main part of a power supplyinterconnect structure of a semiconductor integrated circuit accordingto a first embodiment of the present disclosure.

FIG. 2 is a top view of the power supply interconnect structure.

FIG. 3 is an enlarged view of a circled portion in the power supplyinterconnect structure of FIG. 1.

FIG. 4A illustrates that IR-DROP characteristics improve in the powersupply interconnect structure.

FIG. 4B illustrates IR-DROP characteristics in a conventional powersupply interconnect structure.

FIG. 5 is a top view of a semiconductor integrated circuit having thepower supply interconnect structure and formed as a single chip.

FIG. 6 is a top view of a semiconductor integrated circuit having aconventional power supply interconnect structure and formed as a singlechip.

FIG. 7 is a top view of a semiconductor integrated circuit having apower supply interconnect structure according to a second embodiment.

FIG. 8A illustrates a change in a resistance value when open faultsoccur in a single stack via structure included in the power supplyinterconnect structure.

FIG. 8B illustrates a change in a resistance value when open faultsoccur in a multi-stack via structure included in the power supplyinterconnect structure.

FIG. 9 is a flow chart illustrating formation of the power supplyinterconnect structure.

FIG. 10A illustrates a layout of an interconnect region with low signalinterconnect density in a semiconductor integrated circuit having apower supply interconnect structure according to a third embodiment.

FIG. 10B illustrates a layout of an interconnect region with high signalinterconnect density in the semiconductor integrated circuit.

FIG. 11 is a cross-sectional view of a main part of a power supplyinterconnect structure of a conventional semiconductor integratedcircuit.

FIG. 12 is an enlarged view of a circled portion in the power supplyinterconnect structure of FIG. 11.

FIG. 13 is a top view of the power supply interconnect structure.

DETAILED DESCRIPTION First Embodiment

A first embodiment of the present disclosure will be describedhereinafter with reference to the drawings.

FIG. 1 is a cross-sectional view of a power supply interconnectstructure of a semiconductor integrated circuit according to the presentdisclosure. FIG. 2 is a top view of the power supply interconnectstructure and exemplifies a four-layered structure. In these figures, L1denotes a first interconnect layer, and L4 denotes a fourth interconnectlayer. L2 and L3 denote second and third intermediate interconnectlayers located between the first and fourth interconnect layers L1 andL4.

Reference numeral 1 denotes a first power supply interconnect located inthe first interconnect layer L1. Reference numeral 4 denotes a fourthpower supply interconnect located in the fourth interconnect layer L4.When the first power supply interconnect 1 is connected to the fourthpower supply interconnect 4 as a single power supply interconnect, asecond interconnect 2 and a third interconnect 3 for connecting thepower supply interconnect 1 to the power supply interconnect 4 arelocated in the second and third intermediate interconnect layers L2 andL3. The first to third vias 5, 6, and 7 are located in three insulatinglayers I1-I3. As can be seen from the top view shown in FIG. 2, thefirst to third vias 5-7 are single vias. The second and thirdinterconnects 2 and 3 connected to the single vias have the samecross-sectional shapes, namely the single vias have the same horizontaland vertical length. That is, the single vias 5-7 are borderless viasnot including wide pad portions shown in the conventional structure ofFIG. 13.

As can be seen from FIG. 1, the first single via 5, the secondinterconnect 2, the second single via 6, the third interconnect 3, andthe third single via 7 in a single vertical line are stacked in the samevertical line to form a single borderless stack via 8. The singleborderless stack via 8 forms a connecting portion of the interconnects,which electrically connects the two power supply interconnects, i.e.,the first and fourth power supply interconnects 1 and 4.

Using the single borderless stack via 8 as a single unit (pillar), fiveunits are formed in FIG. 1. These units connects the first power supplyinterconnect 1 to the fourth power supply interconnect 4 to form anelectrically connected single power supply interconnect. Note that,while in FIG. 1, five units are formed with equal spacing, there is noneed to form all of them with equal spacing, and the spacing may beequal and unequal. While the unit includes the single vias 5-7 in thethree insulating layers I1-I3, and the single interconnects 2 and 3 inthe two intermediate interconnect layers L2 and L3, a stack (stacked)via may include, at least, single vias in two insulating layers andinterconnects in the single intermediate interconnect layer.

In this embodiment, the single borderless stack via structure isemployed. As can be seen from FIG. 3, which is an enlarged view of thecircled portion in FIG. 1, the borderless vias 5-7 do not have the padportions 61 shown in the conventional structure of FIG. 12. Thus, evenwhen stack vias in respective units are located with spacing equal tothat of a conventional structure in FIG. 12 and even when aninterconnect separation rule is considered, single signal interconnects10 are located in respective two interconnect tracks 12 provided betweenvias between the units. This structure improves interconnectioncharacteristics as compared to the conventional structure shown in FIG.12 where only the single signal interconnect 62 can be located.

As can be seen from the top view of FIG. 2, interconnect resources usedfor a signal interconnect are 4 vertical tracks and 2 horizontal tracks.Cleary, this structure provides excellent interconnectioncharacteristics as compared to the conventional example shown in FIG. 13where 0 vertical track and two horizontal tracks are used.

Furthermore, as can be seen from the top views of FIGS. 2 and 3, whenthe signal interconnect 10 adjacent to the interconnect 2 of the singleborderless stack via 8 is located, the signal interconnect 10 is locatedon the interconnect track 12. Thus, a distance between the signalinterconnect 10 and the interconnect 2 of the single borderless stackvia 8 is equal to a distance between the signal interconnect 10 andanother signal interconnect 10 adjacent to the signal interconnect 10.By contrast, as in FIG. 12 showing the conventional example, the signalinterconnect 62 is located between the two interconnect tracks 60, noton an interconnect track 60, even when the single signal interconnect 62is located between two multiple vias having the pad portion 61. In thisembodiment, this allows the signal interconnects 10 around the singleborderless stack via 8 on the interconnect tracks 12 to improvecompatibility to the EDA tool.

In the top view of FIG. 2, two single vias 6 are located in apredetermined area of 6 vertical tracks and 3 horizontal tracks. Thenumber of the vias is the same as that of two multiple (double) stackvias in the corresponding area shown in the conventional example of FIG.13. Single vias and multiple vias have the same EM characteristics whenthe rate of EM is determined by a via portion and the numbers of viasare the same. Therefore, in the single borderless stack via structureaccording to this embodiment, EM characteristics are well maintained anddisconnection at a via portion can be reduced.

Furthermore, in the top view of FIG. 2, the two single vias 6 arelocated in the predetermined area. However, in the single borderlessstack via structure according to this embodiment, the single vias 6 maybe located at any position as long as they are located in thepredetermined area. For example, the both single vias 6 may be locatedso that only a single signal interconnect 10 is located between thesingle vias 6 or so that 3 or 4 signal interconnects 10 are locatedbetween the single vias 6.

As described above, the position of the single borderless stack via 8 ishighly flexible in this embodiment. Thus, for example, in thisembodiment, as shown in FIG. 4A, four single vias 6 are widely spacedapart from each other. As a result, the power supply interconnect lengthto the target standard cell 40 which receives power supply can beshortened as compared to the case where four vias 58 forming aconventional multi-stack via are located close to each other, as shownin FIG. 4B. Therefore, in this embodiment, parasitic resistance andIR-DROP can be reduced depending on the short length.

FIG. 5 is a schematic view of a semiconductor integrated circuit havingthe single borderless stack via structure according to this embodiment,and integrated in a single chip. The figure shows an example where allthe vias are single borderless stack vias 20 and the number is 24. FIG.6 illustrates a conventional semiconductor integrated circuit in which 6multi-stack vias of four vias 70 are provided to form a chip. Similar toFIG. 5, the total number of the vias 70 is 24. As can be seen fromcomparison between FIGS. 5 and 6, the semiconductor integrated circuitof FIG. 5 having the single borderless stack via structure according tothis embodiment. It is found that the vias 20 can be equally locatedover the entire surface of the chip as compared to FIG. 6, therebyshortening the power supply interconnect length to the target cell (notshown in FIGS. 5 and 6) receiving power supply and reduce IR-DROP.

Second Embodiment

Next, a second embodiment of the present disclosure will be describedhereinafter with reference to the drawings.

FIG. 7 illustrates a power supply interconnect structure of asemiconductor integrated circuit according to this embodiment. Thefigure shows a semiconductor integrated circuit having two types ofpower supply interconnect structures of: a power supply interconnectstructure in which single borderless stack vias 20 are scattered in alarge number of predetermined places, and a power supply interconnectstructure in which a plurality of multiple (double) stack vias 75 of aplurality of (two in the figure) vias 71 are located as anotherconnecting portion of the interconnects. The detailed structure of themulti-stack via 75 has been shown in FIGS. 11-13 and described in thespecification. Thus, the explanation thereof is omitted. As can be seenfrom FIG. 7, the distances between the plurality of single borderlessstack vias 20 are clearly set longer than the distance between the twovias 71 of the multi-stack via 75.

The region for locating the single borderless stack vias 20 is thesignal interconnect region 30. The region for providing the multi-stackvia 75 is a non-interconnect region 31 to which no signal isinterconnected. This is because, when an open fault of a via occurs, aresistance value is greatly increased in the power supply interconnectstructure with the single borderless stack vias 20. Examples are shownin FIGS. 8A and 8B. When three interconnect layers and two via layersare located in the single stack via structure shown in FIG. 8A, and openfaults of a via occur, a current cannot flow to the unit. Where aresistance value of a single via is R, the combined resistance of twounits is 2R. On the other hand, in the multiple (double) stack viastructure shown in FIG. 8B, an interconnect having a pad portion betweentwo vias having assurance function and the combined resistance is 3/2Rwith small reduction. Therefore, even when a single power supplyinterconnect includes two types of a single borderless stack viastructure and a multi-stack via structure, and open faults of a viaoccur, the combined resistance values of the power supply interconnectcan be maintained low to reduce power supply interconnect defects. Thisenables an increase in the yield and an improvement in interconnectioncharacteristics in the signal interconnect region 30.

FIG. 9 illustrates a flow of the two types of power supply interconnectstructure shown in FIG. 7. In step S1, a required number of single stackvias 20 in design is located in the signal interconnect region 30. Then,in step S2, layout processing of interconnects (i.e., interconnectprocessing) is performed in the signal interconnect region 30. Afterthat, in step S3, existence of an interconnect near the located singlestack vias 20 is determined. When no interconnect exists, the region isdetermined as a non-interconnect region and multi-stack vias 75 arelocated in step S4. The steps S3 and S4 for all the single stack vias 20are repeated and the interconnection is completed in step S5, when thedetermination of existence of interconnects for all the single stackvias 20 are finished.

Third Embodiment

Next, a third embodiment of the present disclosure will be describedhereinafter with reference to the drawings.

FIG. 10 illustrates a power supply interconnect structure of asemiconductor integrated circuit according to this embodiment. In FIG. 7illustrating the second embodiment, only the single borderless stackvias 20 are located in the signal interconnect region 30. In thisembodiment, single borderless stack vias and multi-stack vias arelocated and divided in accordance with the interconnect density of asignal in the signal interconnect region 30.

Each of FIGS. 10A and 10B illustrates a part of a signal interconnectregion. In FIG. 10A, the signal interconnects 43 and 44 are located inthe signal interconnect region. FIG. 10A illustrates a signalinterconnect region having predetermined low signal interconnectdensity, and having much space. In the interconnect, the multi-stack via75 is located in the space. In the figure, the multi-stack via 75includes two vias (double via) 71 as an example.

On the other hand, in the signal interconnect region shown in FIG. 10B,a large number of signal interconnects 45-49 are located with lessspace. The interconnect region has higher signal interconnect densitythan the signal interconnect density in the interconnect region shown inFIG. 10A. The single borderless stack vias 20 are located in theinterconnect region with the high signal interconnect density.

Therefore, in this embodiment, the single borderless stack vias 20 arelocated in the interconnect region shown in FIG. 10B with high signalinterconnect density, the large number of signal interconnects 45-49 areinterconnected with high interconnection efficiency. For example, thesignal interconnects 47 and 49 can be interconnected with smallinterconnect length without rounding around the proximity of the singleborderless stack vias 20.

On the other hand, in the interconnect region shown in FIG. 10A with lowsignal interconnect density, the multi-stack vias 75 are provided. Thenumber of the signal interconnects 43 and 44 is small and there is muchspace, there is no problem in selecting the interconnect path of thesignal interconnects, thereby maintaining high interconnectionefficiency.

Furthermore, the single borderless stack vias 20 and the multi-stackvias 75 are connected to power supply interconnects (i.e., the first andfour power supply interconnects 1 and 4 shown in FIG. 1) in parallel.Thus, when open faults of a via occur, the resistance value of the powersupply interconnect can be maintained low as described in the secondembodiment, thereby increasing the yield of the chip.

As described above, the present disclosure includes a single borderlessstack via as a connecting portion of interconnects electricallyconnecting interconnects of different interconnect layers. Thus, thepresent disclosure provides more excellent interconnectioncharacteristics and a more largely reduced chip area than a multi-stackvia of double or more via having a wide pad portion. This improvesIR-DROP characteristics and reliably locate signal interconnects arounda single borderless stack via on interconnect tracks, thereby improvingcompatibility to an EDA tool. Therefore, the present disclosure isuseful as power supply interconnect structures of various semiconductorintegrated circuits.

What is claimed is:
 1. A power supply interconnect structure of asemiconductor integrated circuit comprising: power supply interconnectslocated in two different interconnect layers with at least one singleintermediate interconnect layer interposed between the differentinterconnect layers; and a single borderless stack via electricallyconnecting the power supply interconnects located in the twointerconnect layers to form a connecting portion of the interconnects,wherein the single borderless stack via forming the connecting portionof the interconnects includes: single vias located in respective two ormore insulating layers located between the two interconnect layers, andan interconnect located in each of the at least one intermediateinterconnect layer, and having a same cross-sectional shape as thesingle vias of the insulating layers, and the single vias of theinsulating layers and the interconnect of the at least one intermediateinterconnect layer are alternately layered in a same vertical line andelectrically connected to form a unit.
 2. The power supply interconnectstructure of claim 1, wherein the unit of the single borderless stackvia includes: single vias located in respective three insulating layers,and interconnects located in respective two intermediate interconnectlayers interposed between the three insulating layers.
 3. The powersupply interconnect structure of claim 1, wherein multiples ones of theunit of the single borderless stack via are formed, and distancesbetween the units are equal.
 4. The power supply interconnect structureof claim 1, wherein multiple ones of the unit of the single borderlessstack via are formed, and distances between the units are equal andunequal.
 5. The power supply interconnect structure of claim 1, whereinmultiple ones of the unit of the single borderless stack via are formed,and a first signal interconnect is located in a region between twoadjacent ones of the units.
 6. The power supply interconnect structureof claim 5, wherein a distance between the single borderless stack viaand the first signal interconnect is equal to a distance between thefirst signal interconnect and a second signal interconnect adjacent tothe first signal interconnect.
 7. A power supply interconnect structureof a semiconductor integrated circuit comprising: power supplyinterconnects located in two different interconnect layers with at leastone single intermediate interconnect layer interposed between thedifferent interconnect layers; and a single borderless stack viaelectrically connecting the power supply interconnects located in thetwo interconnect layers to form a connecting portion of theinterconnects, the single borderless stack via forming the connectingportion of the interconnects; and a multi-stack via configured toelectrically connect the power supply interconnects located in the twointerconnect layers to form another connecting portion of theinterconnects.
 8. The power supply interconnect structure of claim 7,wherein the multi-stack via includes: a plurality of vias located inrespective two or more insulating layers located between the twointerconnect layers, and an interconnect located in each of the at leastone intermediate interconnect layer and having a pad portion to includethe plurality of vias in the two or more insulating layers inside whenviewed from above, and the plurality of vias of the insulating layersand the interconnect of the at least one intermediate interconnect layerare alternately layered in a same vertical line and electricallyconnected.
 9. The power supply interconnect structure of claim 7,wherein the single borderless stack via forming the connecting portionof the interconnects is located in a signal interconnect region, and themulti-stack via forming the other connecting portion of theinterconnects is located in a non-interconnect region to which a signalis not interconnected.
 10. The power supply interconnect structure ofclaim 7, wherein the multi-stack via forming the other connectingportion of the interconnects is located in a region of the signalinterconnect region having predetermined signal interconnect density,and the single borderless stack via forming the connecting portion ofthe interconnects is located in an interconnect region of the signalinterconnect region, which has signal interconnect density higher thanthe predetermined density.
 11. The power supply interconnect structureof claim 9, wherein multiple ones of the single borderless stack via arelocated in a plurality of places, and a distance between the multipleones of the single borderless stack via is longer than a distancebetween the plurality of vias in a same insulating layer of themulti-stack via.
 12. The power supply interconnect structure of claim 1,further comprising: the single borderless stack via forming theconnecting portion of the interconnects; and a multi-stack viaconfigured to electrically connect the power supply interconnectslocated in the two interconnect layers to form another connectingportion of the interconnects.
 13. The power supply interconnectstructure of claim 12, wherein the unit of the single borderless stackvia includes: single vias located in respective three insulating layers,and interconnects located in respective two intermediate interconnectlayers interposed between the three insulating layers.
 14. The powersupply interconnect structure of claim 12, wherein multiples ones of theunit of the single borderless stack via are formed, and distancesbetween the units are equal.
 15. The power supply interconnect structureof claim 12, wherein multiple ones of the unit of the single borderlessstack via are formed, and distances between the units are equal andunequal.
 16. The power supply interconnect structure of claim 12,wherein multiple ones of the unit of the single borderless stack via areformed, and a first signal interconnect is located in a region betweentwo adjacent ones of the units.
 17. The power supply interconnectstructure of claim 16, wherein a distance between the single borderlessstack via and the first signal interconnect is equal to a distancebetween the first signal interconnect and a second signal interconnectadjacent to the first signal interconnect.